“…In taking perceptual practice as a key analytical framework for investigating engineering work, we draw on traditions in both science and technology studies (Alac̆, 2008; Baim, 2018; Daston and Galison, 2007; Latour, 1986; Lynch, 1985) and interaction analysis (Goodwin and Goodwin, 1996; Lindwall and Lymer, 2017; Stevens and Hall, 1998) that have argued for an approach to perception as a situated social practice rather than an individual biological fact. Defects are not natural, pre-given aspects of an environment or product; rather, defects emerge in relation to modes of what Stevens and Hall (1998) call ‘disciplined perception’, a term that draws attention both to the particular forms of perception that support claims to knowledge and expertise (Carr, 2010; Goodwin, 1994) as well as to the fact that these forms of perception are learned practices (Baim, 2018; Butler, 2018; Goodwin, 1997; Jasanoff, 1998; Vertesi, 2012). It was because engineers had learned particular ways of looking at and assessing steel products and production methods that certain perceptible phenomena became recognizable as defects.…”